THE PARTHENOGENETIC EFFECT OF ECHINODERM 

 EGG-SECRETIONS ON THE EGGS 

 OF NEREIS LIMBATA. 



ALVALYN E. WOODWARD. 



(From the Marine Biological Laboratory at Woods Hole and the Zoological 

 Laboratory of Amherst College.) 



Various methods for inducing development in the eggs of 

 Nereis limbata have been tried, but, until now, only two have 

 been successful. Fischer ('03), working in Loeb's laboratory, 

 found that Nereis eggs would divide and develop to the trocho- 

 phore stage if treated for half an hour with sea-water which 

 had been made hypertonic by the addition of NaCl, KC1 or 

 sugar. Just ('15) obtained the same results by putting the eggs 

 into sea-water warmed to 35 or 36 C. Since all other methods 

 tried had been unsuccessful, Nereis acquired the reputation of 

 being refractory to parthenogenetic methods. 



Because of this reputation, I decided to see whether or not 

 development could be induced by means of the substance secreted 

 into sea-water by echinoderm eggs. The experiments, as shown 

 in the table, were successful. In performing them, fresh "dry" 

 Nereis eggs were allowed to stand ten minutes or more in the 

 secretion and then transferred to sea-water, where a large pro- 

 portion would exude jelly, form fertilization membranes, and 

 become mature. Some of these, continuing development, would 

 divide, form normal trochophores, and, finally, small worms, in 

 every external appearance like those resulting from sperm ferti- 

 lization. These have been kept until eighteen days old. It 

 takes these parthenogenetic eggs about twice as long to reach a 

 given stage as it does the sperm controls, a fact which serves as 

 a nice check against accidental contamination with sperm. 



Not only is development brought about by egg secretions, 

 but the same effect may be obtained by treating Nereis eggs 

 with the lipolysin obtained from the secretions (Woodward, '18). 



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